This invention relates to the economical manufacture of a welded gate valve assembly in which component parts thereof are made of stamped metal. The economy of manufacture and the sealing effect of the invention are so great that it is possible to provide a gate valve assembly which may be placed in service for a long time and, when its useful life is at an end, simply thrown away and replaced by a similar economical gate valve assembly. The gate valve assembly of this invention is characterized in that component parts thereof are fabricated economically as stamped metal parts; and that these component parts are welded together to form the completed gate valve assembly. In Canadian patent 919152, assigned in common herewith, welding is used during the manufacture of the gate valve assembly and in particular in conjunction with the gate valve body and may also be used to weld casing halves together. A separate cover assembly, secured in place by nuts and studs, however, is taught inasmuch as this is necessary for manufacturing purposes. The Russian patent 819,475 of 04/81 teaches the manufacture of a gate valve assembly from component parts which are of stamped or pressed steel form and are welded together. The component parts, however, are of extremely complex form and there are many of them, with the result that the economy of manufacture suffers.
The gate valve assembly of this invention forms a very efficient seal and, to this end, it incorporates a wedge-shaped valve body assembly having resilient valve-sealing elements which are made of such material as to be sensitive to destruction or detrimental effect from excess heat during manufacture of the gate valve of this invention. The valve body itself is formed of two stamped metal halves which are welded together and the valve body assembly is completed by sandwiching a heat-sensitive resilient disc between each side of the valve body and a circular plate, the plate in each case being riveted to the respective valve body side after the valve body has cooled from welding so that the heat-sensitive material is not damaged. Unfortunately, if such a valve body assembly is used, the heat-sensitive valve-seating elements thereof cannot be subjected too close to a weld seam being formed while in a closed welding environment during manufacture of the valve assembly. Hence the use of the separate and removable cover assembly of the noted Canadian patent 919152 which teaches the introduction of the heat-sensitive material (when used) into the interior of the casing subsequent to any welding operation. The Russian patent does not disclose the use of a valve body assembly employing vulnerable valve-seating elements and hence teaches nothing concerning protection thereof.
The necessity for the aforesaid protection of the heat-sensitive valve-seating elements arises by reason of the fact that at some point in the manufacture of the gate valve assembly, the valve body assembly to which the heat-sensitive elements are sandwiched must be confined within an enclosed environment defined by the casing and the cover components of the gate valve assembly, whereupon welding between components must be carried out which could easily cause such heat build-up within that environment as to damage the heat-sensitive elements if the weld seam passes in too close proximity to the heat-sensitive elements. In addition, there will be at least some metal-to-metal contact between the valve body assembly and other components during a final welding step of manufacture which could effect direct heat transfer to the heat-sensitive elements and thereby augment the possibility of damage due to the heat build-up. Thus, in any embodiment of the invention where the likelihood of such damage is present, the manufacturing technique of this invention makes it possible to reposition or move the heat-sensitive elements during final welding to alter or change the proximity of the valve body assembly relative to the weld seam.
Accordingly, a primary object of the invention is to protect the heat-sensitive elements of a valve body assembly from damage during manufacture wherein stamped metal components are welded together to effect the final assembly.
It is of primary concern in connection with this invention to provide a method of manufacturing a gate valve assembly comprised substantially wholly of stamped steel components which are few in number and which lend themselves to simple and economical steps of manufacture and wherein heat-sensitive elements are also used which are protected from damage during manufacture. In association with the method, the sequence of steps employed which includes the use of a special fixture for locating the components for welding, is such as to protect the heat-sensitive elements to a maximum degree.
An object of this invention concerns the method of making a gate valve assembly which comprises the steps of: mating two stamped metal valve body halves while capturing an actuating nut between the mated halves; welding the mated valve body halves together to provide a wedge-shaped metal valve body with actuating nut captured therebetween; placing heat-sensitive resilient discs against converging opposite sides of the wedge-shaped metal valve body and mechanically sandwiching such heat-sensitive resilient discs against opposite sides of the metal wedge-shaped valve body to leave circumferential margins of the heat-sensitive resilient discs exposed for sealing purposes to provide a valve body assembly with actuating member captured thereby; inverting the valve body assembly and confining it within a closed environment defined by stamped metal components which, when welded together with the valve body assembly therewithin form a completed gate valve assembly, while supporting and locating the valve body assembly while in minimal contact with the stamped metal components; and then welding the confining stamped metal components together to provide a completed gate valve assembly.
It is preferred that the confining stamped metal components comprise a stamped metal cover to which an actuating spindle sleeve has been welded for receiving the actuating spindle cooperating with the actuating nut, and stamped metal halves forming casing components. The fixture of this invention holds the cover in inverted position with the actuating spindle and actuating nut engaged to support and locate the inverted valve body assembly on the inverted cover and to allow the casing halves to be mated and welded and then to be placed while inverted to surround the inverted valve body assembly in guiding relation thereto and located relative to the inverted cover for final welding.